1. Field of the Invention
The present invention relates to making ground connections to printed circuit boards, and more particularly to a contacting element composed of an electrically conductive material which exerts a restoring force when deformed. This contacting element is compressed between a metal chassis and a printed circuit board to form a ground connection between the printed circuit board and the chassis.
2. Related Art
The business of manufacturing computer systems, and especially personal computer systems, has become very cost-competitive. Because most personal computers are built around identical microprocessors and memory chips, there is presently very little technological differentiation between personal computer systems produced by different manufacturers. Hence, competition between manufacturers is primarily focussed on price. This has driven profit margins down sharply, and has increased competition to assemble computer systems cheaply.
The cost of assembling a computer system can be reduced by simplifying or automating the assembly process. One manufacturing step that has so far been hard to automate is the process of connecting a printed circuit board, such as a motherboard, to a computer system chassis. This connection must typically be made so that the printed circuit board is reliably grounded to the computer system chassis. Referring to FIG. 1, motherboard 100 is mounted into chassis 112 of personal computer system 110 using a contacting element to make a ground connection between motherboard 100 and the chassis 112.
Computer manufacturers typically fasten a motherboard to a computer system chassis by screwing the motherboard to the chassis, so that the printed circuit board is grounded to the chassis by an electrical contact. This electrical contact can be made through a screw, or through contacting surfaces on the printed circuit board and the chassis, which are brought together when the printed circuit board is screwed to the chassis.
This process of screwing a motherboard to the chassis is very time-consuming. An assembly line worker must manually insert and screw down as many as six screws in order to fasten a motherboard to a computer system chassis. Unfortunately, the process of screwing the motherboard to the chassis requires fine motor control, and is consequently hard to automate.
Furthermore, the process of screwing a motherboard into a computer system chassis can potentially cause damage to the computer system. An assembly line worker may slip while operating a screwdriver, and the screwdriver or the screw may cause damage to the printed circuit board. The assembly line worker may also inadvertently drop a screw into the computer system, where the screw may be hard to locate, and may cause electrical shorting.
Some computer manufacturers have eliminated the step of screwing motherboard 100 to chassis 112 by instead sliding motherboard 100 into a mount 200 on a chassis 112. Referring the FIG. 2, mount 200 may be formed by cutting a tab from chassis 112, and bending the tab so that it extends away from chassis 112. Note that the mount 200 includes a slot for receiving motherboard 100.
Referring the FIGS. 3A and 3B, a printed circuit board 300 (such as motherboard 100) may be fastened to mount 200 by inserting mount 200 through an opening in printed circuit board 300, and sliding printed circuit board 300 so that it is secured to mount 200. See FIG. 3B. Not shown in FIGS. 3A and 3B is a locking mechanism coupled to chassis 112 that flips up when printed circuit board 300 is slid into place, in order to lock printed circuit board 300 in place.
Referring to FIGS. 4A and 4B, some manufacturers achieve a ground connection between printed circuit board 300 and chassis 112 by means of a pressure contact between fingers 400 and chassis 112. Fingers 400 include a conductive material, which exerts a restoring force when deformed or biased. Referring to FIG. 4B, fingers 400 are bonded to printed circuit board 300 with solder connections 412. When mount 200 is extended through slot 310 in printed circuit board 300, fingers 400, which would normally extend over slot 310, are displaced from their normal position so they exert a force against mount 200. This creates pressure contacts between fingers 400 and mount 200, which create a ground connection between printed circuit board 300 and chassis 112.
Although the above-mentioned method for securing printed circuit board 300 to chassis 112 does not use screws, it has other disadvantages. Fingers 400 must be soldered or otherwise connected onto printed circuit board 300. If this soldering is performed manually, the soldering process can be quite time-consuming and expensive. If the soldering is performed automatically, solder is likely to wick up from solder connection 412 onto the fingers 400. This may cause fingers 400 to be soldered to opposing fingers 410, if fingers 400 are not separated from opposing fingers 410 during soldering.
Furthermore, referring the FIG. 2, the method of forming mount 200 from chassis 112 leaves a hole in chassis 112. Electromagnetic interference from circuitry within chassis 112 can leak out of the chassis through this hole.
What is needed is an apparatus for grounding and securing a printed circuit board to a chassis of a computer system that is free from the disadvantages of using screws and the disadvantages of soldering contacts to a printed circuit board.